[LLVMdev] Linking to LLVM libs from new project

[Lane Schwartz]

Er... so to answer my own question, for posterity, to set up a new
project (based on the sample project) to link to the core LLVM
library, all you need to do is add the following line to the relevant
make file:

LINK_COMPONENTS = core

So for my example below, I added the above line to tools/sample/Makefile.

Perhaps a mention of this could be added to the "Creating an LLVM Project" page?

Thanks,
Lane


On Mon, Apr 14, 2008 at 8:57 PM, Lane Schwartz <dowobeha at gmail.com> wrote:
> Hi all,
>
>  I have a new sample project set up in my llvm/projects directory, and
>  I'd eventually like my frontend to generate an LLVM IR tree. To do so,
>  I believe I need to link to the appropriate LLVM libraries. That's
>  where I'm stuck.
>
>  I can't seem to find any specific documentation that describes how to
>  set up a new project to link to LLVM libraries.
>
>  To get started, I added a couple lines to the tools/sample/main.cpp
>  file in my project:
>
>  #include "llvm/Module.h"
>  ...
>  // Inside main
>  Module* module = new Module("myfirst");
>
>  Not much, but I just want to verify that I can successfully compile
>  and link using an LLVM IR class.
>
>  Presumably, I need to make some additions to configure.ac and the
>  tools/sample/Makefile, but I can't figure out what those changes
>  should be. Since the linker doesn't know how to get the library, I get
>  an error now when I run make:
>
>  $ make
>  llvm[2]: Compiling sample.c for Release build
>  llvm[2]: Building Release Archive Library libsample.a
>  llvm[2]: Compiling calc.cpp for Release build
>  llvm[2]: Building Release Archive Library libcalc.a
>  llvm[2]: Compiling main.cpp for Release build
>  main.cpp: In function 'int main(int, char**)':
>  main.cpp:16: warning: unused variable 'module'
>  llvm[2]: Linking Release executable Sample (without symbols)
>  Undefined symbols:
>   "llvm::Module::Module(std::basic_string<char,
>  std::char_traits<char>, std::allocator<char> > const&)", referenced
>  from:
>       _main in main.o
>  ld: symbol(s) not found
>  collect2: ld returned 1 exit status
>  make[2]: *** [/opt/src-llvm/projects/myproject/Release/bin/Sample] Error 1
>  make[1]: *** [all] Error 1
>  make: *** [all] Error 1
>
>
>  Since there is no configure.ac file or Makefile listed with the
>  Kaleidoscope tutorial (I even looked around the svn repository for
>  one...), I took a look at what Stacker uses, and took the following
>  from the Stacker configure.ac file:
>
>  dnl **************************************************************************
>  dnl * Set the location of various third-party software packages
>  dnl **************************************************************************
>
>  dnl Location of LLVM source code
>  AC_ARG_WITH(llvmsrc,AS_HELP_STRING([--with-llvmsrc],[Location of LLVM
>  Source Code]),AC_SUBST(LLVM_SRC,[$withval]),AC_SUBST(LLVM_SRC,[`cd
>  ${srcdir}/../..; pwd`]))
>  AC_CONFIG_COMMANDS([llvm_src],[],[llvm_src=$LLVM_SRC])
>
>  dnl Location of LLVM object code
>  AC_ARG_WITH(llvmobj,AS_HELP_STRING([--with-llvmobj],[Location of LLVM
>  Object Code]),AC_SUBST(LLVM_OBJ,[$withval]),AC_SUBST(LLVM_OBJ,[`cd
>  ../..; pwd`]))
>  AC_CONFIG_COMMANDS([llvm_obj],[],[llvm_obj=$LLVM_OBJ])
>
>
>  Since I'm trying to use the Module class, I also tried adding this
>  line to tools/sample/Makefile:
>
>  LINK_COMPONENTS = llvmcore
>
>
>  After making those changes, the linking still fails.
>
>  $ make
>  llvm[2]: Compiling sample.c for Release build
>  llvm[2]: Building Release Archive Library libsample.a
>  llvm[2]: Compiling calc.cpp for Release build
>  llvm[2]: Building Release Archive Library libcalc.a
>  llvm-config: unknown component name: llvmcore
>  llvm-config: unknown component name: llvmcore
>  llvm[2]: Compiling main.cpp for Release build
>  main.cpp: In function 'int main(int, char**)':
>  main.cpp:16: warning: unused variable 'module'
>  llvm[2]: Linking Release executable Sample (without symbols)
>  Undefined symbols:
>   "llvm::Module::Module(std::basic_string<char,
>  std::char_traits<char>, std::allocator<char> > const&)", referenced
>  from:
>       _main in main.o
>  ld: symbol(s) not found
>  collect2: ld returned 1 exit status
>  make[2]: *** [/opt/src-llvm/projects/myproject/Release/bin/Sample] Error 1
>  make[1]: *** [all] Error 1
>  make: *** [all] Error 1
>
>  Any tips or pointers would be greatly appreciated. It seems that
>  linking to the LLVM libraries is a pretty common thing that someone
>  starting a new project might want to do. :) I'd love to figure out
>  how.
>
>  Cheers,
>  Lane
>



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